The present disclosure relates to a supply voltage generating circuit and a switching power supply having the circuit. The supply voltage generating circuit provides a supply voltage for a power terminal of a control circuit in the switching power supply. The supply voltage generating circuit includes a switching circuit, a unidirectional conduction circuit and an energy storage circuit. In a time period during which a main power transistor is turned off, the switching circuit is turned off and a rectifying device provides a current to the energy storage circuit through the unidirectional conduction circuit, in a case that the supply voltage is smaller than a predetermined voltage reference; and the switching circuit is turned on and the current output from the rectifying device flows to the switching circuit, in a case that the supply voltage is larger than or equal to the predetermined voltage reference. When the supply voltage generating circuit is used in a switching power supply, the control circuit has improved controllability for supplying electric energy, and the switching power supply has an increased integration level and a simplified circuit structure, and will not be adversely influenced by resonance.
Legal claims defining the scope of protection, as filed with the USPTO.
1. A supply voltage generating circuit for providing a supply voltage to a power terminal of a control circuit in a switching power supply which has a power stage circuit comprising a main power transistor and a rectifying device, said supply voltage generating circuit comprising: a switching circuit, a unidirectional conduction circuit and an energy storage circuit, wherein said switching circuit has a first terminal being electrically coupled to a first terminal of said unidirectional conduction circuit and a current output terminal of said rectifying device, and a second terminal being coupled to a first ground, said unidirectional conduction circuit has a second terminal being coupled to said first ground through said energy storage circuit, in a time period during which said main power transistor is turned off, said switching circuit is turned off and a current provided by said rectifying device flows to said energy storage circuit through said unidirectional conduction circuit, in a case that said supply voltage is smaller than a predetermined voltage reference, and said switching circuit is turned on and said current provided by said rectifying device flows to said switching circuit, in a case that said supply voltage is larger than or equal to said predetermined voltage reference, and said supply voltage is a voltage produced by said energy storage circuit.
2. The supply voltage generating circuit according to claim 1 , wherein said switching circuit comprises a third switch having a first terminal as said first terminal of said switching circuit and a second terminal as said second terminal of said switching circuit.
3. The supply voltage generating circuit according to claim 2 , wherein said third switch is a transistor having a first electrode terminal as said first terminal of said third switch and a second electrode terminal as said second terminal of said third switch.
4. The supply voltage generating circuit according to claim 1 , wherein said unidirectional conduction circuit comprises a first diode having an anode as said first terminal of said unidirectional conduction circuit, and a cathode as said second terminal of said unidirectional conduction circuit.
5. The supply voltage generating circuit according to claim 1 , wherein said energy storage circuit comprises a capacitor having a first terminal as a first terminal of said energy storage circuit and a second terminal as a second terminal of said energy storage circuit.
6. The supply voltage generating circuit according to claim 1 , wherein said switching circuit, said energy storage circuit and said control circuit are electrically coupled to said first ground.
7. A switching power supply, wherein said switching power supply comprises said supply voltage generating circuit according to claim 1 , wherein: said control circuit controls on and off states of said main power transistor of said power stage circuit to generate an electric output signal at an output terminal of said switching power supply.
8. The switching power supply according to claim 7 , wherein said main power transistor and said control circuit are electrically coupled to said first ground.
9. The switching power supply according to claim 7 , wherein said power stage circuit has a boost-type topology or a buck-type topology or a boost-buck-type topology.
10. The switching power supply according to claim 9 , wherein said electric output signal is a constant-voltage signal or a constant-current signal.
11. The switching power supply according to claim 7 , wherein said rectifying device is a first diode with a cathode as said current output terminal.
12. The switching power supply according to claim 7 , wherein said switching power supply comprises an input capacitor having a first terminal being coupled to an input voltage, and a second terminal being coupled to a second ground.
Cooperative Patent Classification codes for this invention. Click any code to explore related patents in that topic.
June 30, 2015
August 8, 2017
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